The present invention pertains to the radio communication art and, more particularly, to an improved time out timer for a radio transmitter.
Time out timers are well known in the radio communication art, and, particularly, communications systems wherein a plurality of mobile stations share a limited number of available radio channels. In such systems, a mobile user can tie up a channel either through intentional continuous transmission or through unintentional transmitter activation or equipment failure. In an attempt to minimize or eliminate this problem, time out timers have been employed which sense the duration of a transmission and disable the transmitter if the transmission duration exceeds a predetermined limit.
With the advent of mobile data terminals, especially those which process and transmit data via the control of a microprocessor, it has been found that a mobile transmitter can tie up a communication channel despite the incorporation of a conventional time out timer. Here, the microprocessor can go into a failure mode whereby the transmitter is keyed at a high repetition rate. Thus, a conventional time out timer which only responds to continuous transmission does not correct such a fault.
In addition, it is desirable to maintain the transmitter disabled until such time as the microprocessor is reset or reinitialized.
Further, it is desirable to disable transmission during the power out interval of the microprocessor since its output during this interval is unpredictable.